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Polymer Brush Collapse under Shear Flow
Inst Laue Langevin, 71 Rue Martyrs, F-38000 Grenoble, France.;Univ Grenoble Alpes, Liphy, 140 Rue Phys, F-38402 St Martin Dheres, France..ORCID iD: 0000-0001-7904-5639
Rhein Westfal TH Aachen, DWI Leibniz Inst Interact Mat, Forckenbeckstr 50, D-52074 Aachen, Germany.;Rhein Westfal TH Aachen, Inst Tech & Macromol Chem, Forckenbeckstr 50, D-52074 Aachen, Germany.;Univ Sheffield, Dept Phys & Astron, Sheffield S10 2TN, S Yorkshire, England..
Acad Sci Czech Republic, Inst Macromol Chem, Vvi, Heyrovsky Sq 2, CR-16206 Prague, Czech Republic..
Univ Paris Saclay, CNRS, CEA, Lab Leon Brillouin, F-91191 Gif Sur Yvette, France..
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2017 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 50, no 3, p. 1215-1224Article in journal (Refereed) Published
Abstract [en]

Shear responsive surfaces offer potential advances in a number of applications. Surface functionalization using polymer brushes is one route to such properties, particularly in the case of entangled polymers. We report on neutron reflectometry measurements of polymer brushes in entangled polymer solutions performed under controlled shear as well as coarse-grained computer simulations corresponding to these interfaces. Here we show a reversible and reproducible collapse of the brushes, increasing with the shear rate. Using two brushes of greatly different chain lengths and grafting densities, we demonstrate that the dynamics responsible for the structural change of the brush are governed by the free chains in solution rather than the brush itself, within the range of parameters examined. The phenomenon of the brush collapse could find applications in the tailoring of nanosensors and as a way to dynamically control surface friction and adhesion.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017. Vol. 50, no 3, p. 1215-1224
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:uu:diva-320464DOI: 10.1021/acs.macromol.6b02525ISI: 000394410200053OAI: oai:DiVA.org:uu-320464DiVA, id: diva2:1091342
Available from: 2017-04-26 Created: 2017-04-26 Last updated: 2018-04-11Bibliographically approved
In thesis
1. Opportunities and challenges of surface scattering at next generation neutron sources
Open this publication in new window or tab >>Opportunities and challenges of surface scattering at next generation neutron sources
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Complex fluids and soft matter are ubiquitously found in the world and all contacts in life are made over surfaces. To describe the mechanical behavior of such substances, rheological methods are used. Flow instabilities are a big challenge in rheology since they will be reflected in the macroscopic variables probed, like e. g. the viscosity. Many such discontinuities may actually originate at the surface. Investigating the properties of liquids in contact with the surface under mechanical load is the main course of the thesis. Neutron reflectometry and GISANS are perfect tools in this context to access the solid liquid interfaces, since they can penetrate many engineering materials and show a comparably large scattering potential at deuterated samples. In this thesis shear was applied on a model solution and neutron scattering techniques were used to investigate the structure under load. The focus was set on the development of the measurement methods themselves to enable new scientific insights in the future. First, by stroboscopic measurements the flux limitations are overcome for oscillatory rheology. By reintegration in the post processing it is shown that kinetic measurements with neutrons are possible with a time resolution below one millisecond. Second, the transformation of grazing incidence data from the laboratory system into q-space is strongly non-linear resulting in a need for re-binning. In this thesis a universal tool has been developed for this purpose. Finally, there is an ongoing discussion on depth sensitive neutron scattering experiments from solid-liquid boundaries. By using emission densities we show that such experiments face severe limitations due to the low absorption cross section of the neutron.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 51
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1666
Keywords
GISANS, data reduction, off-specular, neutron scattering, reflectometry, complex fluids, rheology
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-348348 (URN)978-91-513-0324-6 (ISBN)
Public defence
2018-05-25, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:30 (English)
Opponent
Available from: 2018-05-08 Created: 2018-04-11 Last updated: 2018-05-08

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Korolkovas, AiridasWolff, MaximilianAdlmann, Franz

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